Louisville businessman Matt Bevin has criticized McConnell's conservative credentials and argued that the minority leader had not adequately led the charge to defund President Barack Obama's health care law. That ultimate effort prompted the recent budget stalemate, but the urgency of the debt limit led to a bipartisan deal that was announced Wednesday on the Senate floor.

In an extensive statement, Bevin said McConnell "can always be counted on to sell out conservatives."

"After falsely promising that he would fight to eliminate Obamacare 'root and branch,' Sen. McConnell has instead given us more spending, more borrowing, and the Obamacare train wreck with exceptions for liberal pet interests," Bevin said. "Kentuckians are overwhelmingly opposed to Obamacare. Why does Mitch McConnell refuse to listen to his own constituents?"

In response, McConnell campaign spokeswoman Allison Moore dismissed the criticism and referred to a story from earlier this year about confusion over résumé information on Bevin's LinkedIn page.

"At some point, you'd think Matt Bevin would take a deep breath, stare up at his fake MIT diploma, and wonder whether this is the kind of campaign he envisioned," Moore said.